Magnesium deficiency

Yellowing between the veins of older leaves while the veins stay green. Very common in coco and with soft or RO water.

Symptoms

• Yellowing between the veins of older, lower leaves while the veins stay green.
• Patches may turn brown or rusty later.
• Spreads upwards if not corrected.

Quick checks

• Are older or newer leaves affected? (Older = magnesium; newest = iron.)
• Check feed and run-off pH.
• Are you in coco or on soft or RO water without Mag Cal?

How to fix it

1. 1
   Check

   Correct pH

   Check the basics first: feed and run-off pH (5.5–6.5), EC for this week, watering, climate and light. Keep pH above 5.8 in coco and hydro.

2. 2
   Feed

   Add Mag Cal

   Use Mag Cal at 1 ml per litre with every feed in coco or with soft or RO water.

3. 3
   Monitor

   Judge by new growth

   Give it 3–5 days. Leaves that have already yellowed won't green up fully.

Likely causes

• Coco holding on to magnesium.
• Soft tap water or RO water.
• pH too low, especially below about 5.8 in coco and hydro.
• Cold or waterlogged roots.

What to avoid

• Don't confuse it with iron (newest leaves) or nitrogen (even yellowing).
• Don't add several supplements at once.

Prevention

• Mag Cal every feed in coco, soft or RO water.
• pH in range, calibrated pen.

Monkey products that can help

Mag Cal

Magnesium sits at the heart of chlorophyll; Mag Cal is made for coco and soft or RO water.

1 ml per litre (10 ml per 10 L), for coco and for soft or RO water.

View product →

Products support a healthy plant. They don't replace fixing the cause.

When to get help

If yellowing keeps spreading after a week of correct pH and Mag Cal, email info@monkeynutrients.co.uk with photos and your readings.

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